Explain P - N junction.

P - N junction: If a p- type semiconductor is properly joined to an n-type semiconductor the contact surface that formed is termed as p-n junction. These semiconductor devices consist of one or more p-n junction. P-N junction is fabricated through special techniques that are growing, diffusion and alloying methods. This p-type semiconductor is having positively charged electrons and negative acceptor ions. The n-type semiconductor is containing positive donor ions and negatively charged electrons. While the two pieces are joined together and suitably functioned they form a p-n junction. The moment they make a p-n junction, several of the conduction electrons from n-type material diffuse over to the p- type material and undergo electron hole recombination along with the holes obtainable in valence band. Concurrently holes from p-type material diffuse over to n- type material and undergo hole- electron combination along with the electrons available in the conduction band. Such process is termed as diffusion. If a p-n junction is connected across an electric supply, the junction is said to be under biasing. And the potential difference across the p- n junction, can be applied in two manners, namely- forward and reverse biasing. When the positive terminal of a dc source is connected to p-type, and negative terminal is connected n-type semiconductor of a p-n junction, the junction is as in forward biasing. While the positive terminal of a dc source is linked to n-type, and negative terminal is associated p-type semiconductor of a p-n junction, the junction is as in reverse biasing. By forward bias, a low resistance path is set up in the p-n junction, therefore current flows through the circuit. Along with reverse bias, a high resistance path is established and no current flows through circuit. Such property is best suited for rectification of ac in dc.

p-n Junction